It has been shown that radiopaque powder instilled into the colon of anesthetized dogs moves toward the anus without contraction or changes in pressure in the rectum. The movement of radiopaque powder is affected by secretion of mucus; without mucus it fails to move toward the anus. Our objective is to establish the nature and mechanisms of a new type of motility discovered in dogs' distal colon. This non-contractile motility appears to be a gliding propulsion of material on the surface of the rectum, apparently by mucus. The nature of this movement, its direction, its speed and the influence of drugs on it will be studied in vivo and in vitro.